Fueling nozzle with integral molecular leak sensor

ABSTRACT

An apparatus and process for measuring the concentration of hydrogen gas being transferred through a nozzle from a source container to a destination container and for providing an alert and/or taking action where hydrogen gas leaks may create an unsafe condition. The invention can accurately and reproducibly respond to and measure the absolute hydrogen gas concentration within the nozzle housing using hydrogen gas sensors that are selective only to hydrogen, which do not require the presence of oxygen to operate and which do not saturate when hydrogen safety levels are reached. These sensors are positioned inside the nozzle housing to allow for the direct and immediate knowledge of the presence of hydrogen gas that cannot be safely determined by other means. An apparatus and process for detecting leaks of liquid hydrogen through a nozzle during transfer of liquid hydrogen from a source container to a destination container are also discussed.

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to chemical detection andmore particularly to an apparatus and process for the measurement ofhydrogen, a flammable material, when the hydrogen is being transferredfrom one storage container to another storage container.

[0002] Based on the literature and general good practices to thoseskilled in the art of transferring toxic and/or flammable material fromone storage container to another container, only external “leak”detection devices have been used, i.e., gas detectors that alert theproper personnel once the flammable material has “escaped” to the openenvironment from the supposedly-closed system. For example, when naturalgas is transferred, usually a mercaptan (e.g., tertiary butyl mercaptan,isopropyl mercaptan, normal propyl mercaptan, dimethyl sulfidemercaptan, and methyl ethyl sulfide) is combined with the natural gasflow simply to provide an odor that can be detected by a person in thevicinity of the natural gas leak to alert that person that a leak isoccurring.

[0003] For the past several years, where hydrogen is the flammablematerial being transferred, gas detector devices available on the markethave utilized thermal conductivity technology, electrochemicaltechnologies, metal-oxide semiconductor (MOS) technologies, or opticaltechnologies all of which suffer from the disadvantages discussed below.For example, thermal conductivity sensors may pose an “ignition source”problem that can ignite leaking hydrogen, when the hydrogenconcentration is greater than about 4% per volume; electrochemical andMOS technologies require the presence of oxygen to operate; opticalsensors cannot get wet or be exposed to a wet environment and thereforemust typically be used in a clean and dry environment.

[0004] One type of conventional device used as a flammable gas detectoris the combustible gas indicator (CGI) such as that sold by Mine SafetyAppliances Co. of Pittsburgh, Pa., as well as other safety devicemanufacturers. The CGI is one of the most widely used instruments toprovide a warning to safety responders when flammable substances in theatmosphere begin to approach their explosive limits. Most firedepartments and industrial facilities have such instruments. The CGI isa non-specific detector that detects flammable gases in the atmosphere.Its operation is based upon the catalytic combustion of the flammablegas on a filament in a detector known as a “Wheatstone Bridge”. The CGIis calibrated with a flammable gas (e.g., hexane) using a knownconcentration referenced to NIST (National Institute of StandardTechnology). The burning of this known concentration of the calibrantgas on the filament (relative to a reference “cool” filament) produces asignal, which is directly proportional to this specified concentrationof the calibrant gas. In the field, the detection of a differentflammable gas produces a signal that can be related to the response ofthe calibrant gas by pre-determined “response factors” that are providedby the manufacturer of the instrument. However, as mentioned earlier,this approach cannot be used within the fueling nozzle because of itsmode of operation, because its hot wire-filament, can cause an unsafecondition, by generating a spark source.

[0005] For hydrogen, the flammable detection means requires substantialamounts of oxygen (e.g., >10%) be present, best applied to metal oxidesemiconductor (MOS) sensor technology. This is also not acceptablebecause mixing air, or oxygen, with hydrogen (i.e., 4%-74% hydrogen inair or 4%-90% hydrogen in oxygen) in the presence of an ignition source(e.g., at least 0.02 millijoules), results in a dangerous condition.Currently, MOS-based sensors as primary information providers are widelyused in many fields of technology and industry for environmentalanalysis. The most ardent problems of MOS-based sensor manufacturing arethe reproduction of resistive properties and possibility of theformation of thin film metal oxide sensitive layers in certainconfigurations.

[0006] Another commercial means of flammable gas detection involves useof a catalytic bead sensor (which also requires the presence of oxygen).This type of sensor is made from two separate elements or “beads” thatsurround a wire operating at a high temperature (approximately 450° C.).A first element, the active element, is made by winding a small coil ofwire, sealing it in a ceramic substance, and then coating it with acatalyst to promote a reaction with the gas. The second element, thereference element, is made identical to the active element except inplace of the catalyst, a passivating substance is used to prevent thisbead from reacting with the gas molecules. The reference beadcompensates for changes in ambient temperature, humidity, and pressurevariations. The beads are generally placed in separate legs of aWheatstone bridge circuit. In theory, when gas comes into theenvironment, it has no effect on the passivated bead, but has asignificant effect (primarily in terms of temperature) on the catalyzedbead. The increase in heat increases the resistance; the differencebetween the readings of the wires in the two beads forms the sensorsignal. However, catalytic bead sensors operate above a threshold or“turn-on” voltage corresponding to the bead temperature that can, in thepresence of the catalyst and oxygen, first ignite the gas. As the sensorages, the catalyst slowly deactivates on the bead. The threshold voltagegradually increases, and the sensor sensitivity decreases. At the sametime, changes in the wire coil cause increased zero drift and noise. Theresult is the sensor must be replaced. When a mixture of combustible gasor vapor in air diffuses through the sensor flame arrestor, it oxidizeson the catalytically-treated sensing bead. Since this oxidation reactionis exothermic, it causes an increase in the temperature of this bead (inrelationship to the temperature of the reference bead) and a resultingincrease in the electrical resistance of a small platinum coil embeddedin this bead. The change in resistance in the embedded platinum coil isproportional to the amount of chemical energy released by the oxidationreaction. Electronic circuitry (e.g., a transmitter) immediately detectsthis increase in resistance and reduces electrical power to the beaduntil the original platinum coil resistance is restored. The amount ofelectrical power removed is linearly proportional to the combustible gasconcentration present.

[0007] Electrochemical sensors utilize a technology similar to fuelcells. Fuel cells consist of an electrolyte with an anode on one sideand a cathode on the other. They create electricity by passing a gas(usually hydrogen) over the anode and oxygen over the cathode. The twoelectrodes are separated by an electrolyte. This produces electricity,water, and heat. Electrochemical sensors work the same way. The gaspassing over the electrode creates a chemical reaction and electricalcurrent. The current generated is proportional to the amount of gas inthe cell. In order for these to work, there must be oxygen on the otherside of the cell.

[0008] Various gas sensor configurations are shown in U.S. Pat. No.5,279,795 (Hughes et al.); U.S. Pat. No. 6,293,137 (Liu et al.); U.S.Pat. No. 5,012,672 (McKee); U.S. Pat. No. 4,782,302 (Bastasz), U.S. Pat.No. 5,834,627 (Ricco et al.); and U.S. Pat. No. 5,932,797 (Myneni).

[0009] There remains a need for an apparatus/method that provides forthe measurement of hydrogen levels when transferring hydrogen from onecontainer to another while utilizing a hydrogen sensor that is selectiveonly to hydrogen and does not cross interfere with other species, doesnot rely on temperature differentials (e.g., thermal conductive sensorssuch as catalytic bead sensors), oxygen (e.g., electrochemical and MOSsensors) and does not require a clean and dry environment (e.g., opticalsensors) and which can be positioned inside a nozzle transferring thehydrogen without saturating the sensor.

BRIEF SUMMARY OF THE INVENTION

[0010] A first embodiment of the invention relates to a nozzle fordispensing hydrogen gas from a hydrogen gas source into a container andfor detecting hydrogen gas leaks. The nozzle comprises a housing havinga portion that is adapted for coupling to an opening of the container;and at least one sensor that is positioned inside the nozzle and whereinthe sensor detects the concentration of hydrogen and emits a signalindicative of the concentration of hydrogen.

[0011] A second embodiment of the invention relates to a method fordetecting hydrogen gas leaks during the transfer of hydrogen gas from ahydrogen gas source into a container. The method comprises the steps ofproviding a nozzle, coupled at one end to a transfer line from thehydrogen gas source, and having an output at its other end; positioningat least one sensor inside the nozzle, and wherein the at least onesensor emits a signal indicative of the concentration of hydrogen it isdetecting while hydrogen is being transferred; coupling the at least onesensor to a controller, and wherein the controller receives the signalindicative of the concentration of hydrogen; coupling the output end ofthe nozzle to an opening of the container; initiating transfer ofhydrogen gas from the hydrogen gas source to the container; and alertingan operator or shutting off the transfer of hydrogen gas, by thecontroller, whenever the controller determines that the received signalhas reached or exceeds a predetermined hydrogen concentration.

[0012] A third embodiment of the invention relates to a hydrogen gastransfer monitoring and control system for dispensing hydrogen gas froma hydrogen gas source into a container and for responding to hydrogengas leaks. The monitoring and control system comprises: at least onenozzle that is coupled to a hydrogen gas source via a transfer line andcontrol valve; the nozzle comprises: a housing having a portion that isadapted for coupling to an opening of the container; and at least onesensor that is positioned inside the nozzle, wherein the sensor detectsthe concentration of hydrogen and emits a signal indicative of theconcentration of hydrogen; and a controller, electrically-coupled to theat least one sensor and coupled to the control valve, and wherein thecontroller alerts personnel and/or controls the control valve wheneverthe controller determines that the signal has reached or exceeds apredetermined hydrogen concentration.

[0013] A fourth embodiment of the invention relates to a nozzle for usein a transfer system for dispensing liquid hydrogen from a liquidhydrogen source into a container and for detecting the undesirable entryof oxygen into the system. The nozzle comprises: a housing having aportion that is adapted for coupling to an opening of the container; andan oxygen sensor, positioned inside the nozzle, for detecting theconcentration of oxygen when the liquid hydrogen is not flowing andwherein the sensor emits a signal indicative of the concentration ofoxygen.

[0014] A fifth embodiment of the invention relates to a method fordetecting the undesirable entry of oxygen into a transfer system thattransfers liquid hydrogen from a liquid hydrogen source into acontainer. The method comprises the steps of: providing a nozzle,coupled at one end to a transfer line from the liquid hydrogen source,and having an output at its other end; positioning an oxygen sensorinside the nozzle and coupling the sensor to a controller; coupling theoutput end of the nozzle to an opening of the container; emitting asignal, by the oxygen sensor, indicative of the concentration of oxygenin the transfer system before liquid hydrogen begins transferring, andwherein the signal is received by the controller; and preventing thetransfer of liquid hydrogen until the oxygen is removed from thetransfer system.

[0015] A sixth embodiment of the invention relates to a nozzle for usein a transfer system for dispensing liquid hydrogen from a liquidhydrogen source into a container and for detecting the undesirable entryof oxygen into the system. The nozzle comprises a housing having aportion that is adapted for coupling to an opening of the container andanother portion coupled to a transfer line from the liquid hydrogensource, wherein the transfer line comprises an oxygen sensor therein,and wherein the oxygen sensor detects the concentration of oxygen whenthe liquid is not flowing and wherein the sensor emits a signalindicative of the concentration of oxygen.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0016] The invention will be described by way of example with referenceto the accompanying drawings, in which:

[0017]FIG. 1 is a block diagram showing the hydrogen fueling nozzle ofthe present invention used with a monitoring & control system fortransferring hydrogen between containers;

[0018]FIG. 2 is a cross-sectional view of a high pressure gas nozzleusing a double block and bleed configuration;

[0019]FIG. 3 is a cross-sectional view of the present invention showingthe high pressure gas nozzle of FIG. 2 using the internal hydrogen gas(IHG) sensors;

[0020]FIG. 4 is a functional diagram of an exemplary hydrogen fuelingstation that utilizes the present invention;

[0021]FIG. 5 is a partial cross-sectional view of the nozzle of thepresent invention coupled to the fueling port of a vehicle;

[0022]FIG. 5A is a cross-sectional of the output end of the nozzle,taken along line 5A-5A of FIG. 3, showing how three IHG sensors arearranged at that nozzle location to ensure that any hydrogen present atthat location will be detected regardless of the orientation of thenozzle;

[0023]FIG. 6 is a profile of the hydrogen fueling process, with respectto a hydrogen sensor located at the nozzle shroud;

[0024]FIG. 7 is a functional diagram of a hydrogen gas sensor usedinside the nozzle of the present invention; and

[0025]FIG. 8 is a functional diagram of a nozzle for transferring liquidhydrogen.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention provides an apparatus and method foraccurately measuring the hydrogen concentration within a hydrogenfueling nozzle during transfer of hydrogen from one storage container toanother storage container and automatically alerting and/or safelycontrolling such transfer as required.

[0027] As shown in FIG. 1, hydrogen is transferred from a firstcontainer 1 to a second or “destination” container 2 via a transfer line3 and the fueling nozzle 20. The first container 1 may comprise anysupply source such as a pressure vessel (wherein a pressure vessel isdefined as a closed container capable of withstanding internal pressuregreater than ambient pressure, and in as used in this Specification,typically less than 900 atmospheres), or hydrogen generator such as ahydrolysis unit or a reformer, a gas compressor, or a liquid hydrogenpump. The second container 2 may comprise a pressure vessel.

[0028] Furthermore, this fueling nozzle 20 forms part of a monitoringand control system 22 that also comprises a controller 26 and alarm 28.As will be discussed in detail later, the fueling nozzle 20 informs, viathe use of molecular sensors 100 internal to the nozzle housing, thecontroller 26 of the absolute concentration of the hydrogen in transitand the controller 26 can activate a series of alarms 28, if necessary,and can even stop the flow of the hydrogen, where required, bycontrolling, e.g., a transfer valve 4. In particular, the molecularsensors 100 emit a signal indicative of the current concentration ofhydrogen to the controller 26.

[0029] As used throughout this Specification, the term “internal” means“within or on the nozzle” and excludes any location off of the outsidesurface of the nozzle. To that end, as will be discussed in detailbelow, the term “internal” includes any and all locations inside or onthe nozzle such as but not limited to the normal flow path of thehydrogen gas through the nozzle, the walls of the nozzle, seals in thenozzle, shafts, valves, shrouds, rings, etc. that form any portion ofthe nozzle.

[0030] It should be understood that the preferred embodiment of thefueling nozzle 20 is for use with hydrogen gas transfer. However, it iswithin the broadest scope of this invention to include a fueling nozzle,also using internal sensors, for transferring liquid hydrogen from onecontainer to another container; the discussion of such a fueling nozzlefor transferring liquid hydrogen will be discussed later.

[0031]FIG. 3 shows a cross-sectional view of the nozzle 20 of thepresent invention which comprises a typical high pressure gas nozzle 202(FIG. 2) that includes internal hydrogen gas sensors 100, and wherebythe normal flow path (NFP) of the hydrogen gas is shown. As will bediscussed in detail later, one of the important features of the presentinvention 20 is that these hydrogen sensors 100 are positioned internalto the gas nozzle 202, not external to the nozzle housing. It should beunderstood that the high pressure gas nozzle 202 (FIG. 2) is shown byway of example only and that any high pressure gas nozzle 202 could beused.

[0032] In particular, the exemplary gas nozzle 202 depicted in FIG. 2comprises a “double block and bleed nozzle” construction having an input204, an output 206, a vent 208, and a control handle 210. In the presentinvention 20 (FIG. 3), the internal hydrogen gas sensors 100 arepositioned at locations within the nozzle housing 202 that may be proneto leaks, i.e., locations having a seal, seat and/or O-ring. Forexample, the following are candidate hydrogen gas sensor locationsinside the nozzle housing 202: Location IHG H₂ Reference SensorConcentration Nozzle Housing 20 Location Number Number Range inletmodule housing 202A 100A 0-50K ppm inlet valve 202B 100B 0-50K ppmO-ring 202C 100C 0-50K ppm inlet valve seal seat 202D 100D 0-50K ppmhandle block 202E 100E 0-50K ppm Bushing sub-assembly 202F 100F 0-50Kppm eccentric shaft 202G 100G 0-50K ppm wear ring 202H 100H 0-50K ppmO-ring 202I 100I 0-50K ppm valve seal 202J 100J 0-50K ppm seal tensioner202K 100K 0-50K ppm O-ring 202L 100L 0-50K ppm O-ring 202M 100M 0-50Kppm step seal 202N 100N 0-50K ppm Protection sleeve 202O 100O 0-50K ppmShroud 202P 100P 0-50K ppm

[0033] By positioning these hydrogen gas sensors 100 at these internalnozzle locations, the sensors 100 can accurately detect the absoluteconcentration of hydrogen gas at these internal locations and thereforepermit the monitoring and control system 22 to automatically respond(when necessary) to these detected levels. In addition, all of thesesensors 100 are positioned in the nozzle 20 for ease ofmaintenance/removal.

[0034] For example, as shown in FIG. 4, a hydrogen fueling station isdepicted using a plurality of these fueling nozzles 20 which includethese internal hydrogen gas sensors 100 (hereinafter “IHG sensors 100”).Each fueling nozzle 20 is coupled to a common hydrogen source 1A viarespective control valves 4A. Each IHG sensor 100 is independentlycoupled to the controller 26 for providing an electrical signal fromeach sensor 100 in the nozzle 20 representing the respective hydrogenconcentration detected, as well as for providing excitation (e.g.,24VDC) to the sensor 100. A wire harness 32 represents all of thesignal/power cabling from each of IHG sensors 100 to the controller 26for each nozzle 20. A control cable 34 is coupled between the controller26 and each control valve 4A that allows the controller 26 to shutdown aparticular hydrogen transfer, if necessary. Vehicles 10 (or otherdestination hydrogen containers) can be then be positioned adjacent acorresponding a fueling nozzle 20. As shown clearly in FIG. 5, thenozzle output 206 is adapted for coupling (for effecting a tight seal)to a fueling port 14 of the vehicle's hydrogen tank 2A.

[0035] It should be noted that where the fueling nozzle 20 can becoupled to the fueling port 14 in any position rotated around its axis101 (FIG. 3), it is possible that an IHG sensor, e.g., IHG sensor 202P,could be temporarily located at an elevation beneath the hydrogen gasleak point, thereby resulting in that leak being undetected by IHGsensor 202P. To prevent this from occurring, it may be necessary toposition three IHG sensors around that particular location within thenozzle 20. For example, as shown in FIG. 5A, three IHG sensors, namely,IHG sensor 202P, 202P′ and 202P″ are displaced 120° around the insidecircumference of the shroud 100P. Using this configuration, no matter inwhat angular position the nozzle 20 is coupled to the fueling port 14A,at least one of the IHG sensors 202P, 202P′ and 202P″ would detect aleak at that location, e.g., the location most likely to experience aleak would be at location 25 (FIG. 5), the coupling interface betweenthe nozzle 20 and the fueling port 14.

[0036]FIG. 6 depicts a typical hydrogen fueling process over time basedon IHG sensor 100P at the nozzle shroud 202P which surrounds the nozzleoutput 206. In particular, before the nozzle 20 is coupled to thefueling port 14, IHG sensor 100P should only be detecting backgroundhydrogen levels (BHL; see FIG. 6); this is defined as the pre-fuelingstage, t_(PF). As the nozzle 20 is coupled to the fueling port 14, IHGsensor 100P begins detecting the hydrogen concentration emitted from thefueling port 14 itself which causes the detected hydrogen concentrationlevel to spike, during this nozzle coupling period, t_(NC). Once thenozzle 20 is securely coupled to the fueling port 14, the fuelingperiod, t_(F), begins when the operator manipulates the handle 210wherein hydrogen gas is delivered to the vehicle fuel tank 2A. As thehydrogen flow enters the nozzle 20, the pressure increases and somehydrogen may leak around the seal which is detected by the IHG sensor100P, which is indicated by the slowly rising hydrogen concentrationshown in FIG. 4. When the vehicle fuel tank 2A is filled, or otherwiseterminated by the operator manipulating the handle 210, the operatorthen de-couples the nozzle 20 (t_(ND)) which causes the detectedhydrogen level to spike. Once the nozzle is completely de-coupled, anyfinite amount of hydrogen gas released then dissipates; as a result, asshown in FIG. 6, during this “after fueling” period, t_(AF), the IHGsensor 100P detects this decreasing hydrogen concentration level whichreturns to the BHL.

[0037] As can be appreciated, the key to the nozzle 20 of the presentinvention, as well as the monitoring and control system 22, is the IHGsensor 100. In order to accurately account for hydrogen leaks in aclosed environment (e.g., low oxygen content) with high precision, thesesensors 100 must:

[0038] be able to operate without the need for oxygen;

[0039] avoid initiating an unsafe condition (e.g., avoid acting as anignition source);

[0040] respond to and be corrected for pressure changes;

[0041] respond to a broad range of hydrogen concentrations in a wet(humidity 0

[0042] 100% and condensation) environment;

[0043] respond to hydrogen changes without interference or falsepositive responses from other gas materials in and around the naturalenvironment (e.g., hydrocarbons (such as methane or ethane), carbonmonoxide, etc.);

[0044] respond to hydrogen concentration changes in a broad range ofenvironmental temperature conditions (−40° C. to 85° C.);

[0045] respond to hydrogen concentration changes in a fast and efficientmanner to differentiate with a high degree of confidence a 10% absoluteH2 concentration increase from 100 ppm to >99%; and

[0046] respond to hydrogen at a constant concentration and not becomesaturated to the point where performance is sacrificed.

[0047] A hydrogen gas sensor that can achieve these performancecharacteristics is presently sold under the tradename ROBUST HYDROGENSENSOR™ by H2SCAN, LLC of Valencia, Calif. The H2SCAN sensor utilizes atwo-part hydrogen-detection mechanism that permits the sensor to detecthydrogen concentrations over a broad range while remaining exclusivelyselective to hydrogen. In particular, as shown in FIG. 7, the H2SCANsensor is an ASIC (application specific integrated circuit) comprising ahydrogen-sensing field effect transistor 104 (FET—also referred to as aMOS or MIS (metal-insulator-semiconductor) transistor/capacitor) fordetecting low levels of hydrogen (e.g., 1 ppm-5000 ppm) and apalladium-nickel (Pd—Ni) chemiresistor 102 for detecting high levels ofhydrogen (e.g., 2500 ppm-1×10⁶ ppm).

[0048] Furthermore, each of these two hydrogen-detecting mechanisms102/104 can be temperature-compensated and pressure-compensated byrespective on-board circuitries 106/108. The construction and operationof the H2SCAN sensor is set forth in U.S. Pat. No. 5,279,795 (Hughes etal.) whose entire disclosure is incorporated by reference herein. Inaddition, Sandia National Laboratories Report SAND2000-8248, June 2000,entitled “A Small Form Factor Solid-State Hydrogen Sensor Package” by S.E. Fass and G. R. Dulleck provides further details about the H2SCANsensor design and operation.

[0049] This H2SCAN sensor structure is unique in that only hydrogenatoms can diffuse into the sensor material to trigger the changes inelectrical behavior, i.e., the H2SCAN sensor is selective for hydrogen.Alloying palladium with nickel prevents phase transitions in the thinfilms at high H₂ overpressures, making this sensor suitable for chemicalprocess conditions. In particular, as stated in the product literaturefor the H2SCAN sensor, entitled “The DCH Robust Hydrogen Sensor™”, thesensor:

[0050] . . . consists of a thin film of palladium-nickel (Pd/Ni)deposited on a silicon substrate that acts like a resistor in thepresence of hydrogen. The lattice inherent in the Pd/Ni absorbs hydrogenmolecules. As the number of hydrogen molecules increases in the lattice,the resistance of the Pd/Ni increases in direct correlation to theamount of hydrogen present. The thin film is embedded into an integratedcircuit, which interprets this resistance and displays the hydrogenconcentration to the operator. It also generates a voltage signal indirect correlation to the amount of hydrogen that can be interpreted byan external monitoring/control system. Since palladium only behaves inthis manner with hydrogen, there is no cross-sensitivity of the sensorwith any other elemental or compound gas . . .

[0051] Thus, no oxygen or other gas is required for the hydrogen-sensingFET 104/Pd—Ni chemiresistor 102 to function. Furthermore, the Pd—Nichemiresistor 102 can continue to accurately detect hydrogenconcentrations (e.g., 2500 ppm-1×10⁶ ppm), whereas other conventionalhydrogen sensors would otherwise saturate. This last feature isimportant because by not saturating, the H2SCAN sensor can continue toprovide accurate hydrogen concentration levels to the controller 26;this uniquely allows the controller 26 to allow hydrogen transfer inthose lines still operating safely while taking appropriate action(setting an alarm, shutting down a particular transfer, etc.) fortransfers that have reached a first safety level (e.g., 10,000 ppm),thereby avoiding a “worst case scenario” by implementing anacross-the-board shutdown of all transfers; in contrast, becauseconventional hydrogen sensors saturate at the first safety level, thosemonitoring systems must implement the worst case scenario action andshutdown all transfers.

[0052] It should be understood that in adapting the H2SCAN sensor foruse internal to the nozzle 20 of the present invention, a newconfiguration of the H2SCAN sensor has been defined. Only one of the twohydrogen-detecting mechanisms 102/104 needs to be used on any of the IHGsensors 100 during nozzle 20 operation. In other words, each of the IHGsensors 100 is using only one of the hydrogen-detecting mechanisms whilethey are monitoring conditions inside the nozzle 20. In particular, theIHG sensors 100 (100B-100P) located at internal nozzle locations202B-202P require only the Pd—Ni chemiresistor 102 while the IHG sensor100 (100A) at location 202A (a coupling location between the nozzle 20and the transfer line 3A) requires only the hydrogen-sensing FET 104.These particular hydrogen-detecting mechanisms are established based onthe conditions at these nozzle locations.

[0053] For example, if a hydrogen gas leak occurs at locations202B-202P, the hydrogen-sensing FET 104 would be quickly saturated andno longer provide an accurate measurement of the absolute hydrogenconcentration. On the other hand, IHG sensor 100 (100A) at nozzlelocation 202A, which forms one of the most leak-tight points in thefueling system, hydrogen concentration levels at all times during thefueling process remain in the low range (e.g., 1 ppm-5000 ppm) where thehydrogen-sensing FET 104 accurately operates and to which the Pd—Nichemiresistor 102 could not accurately detect. Thus, one of the novelaspects of the present invention 20 is that the IHG sensors 100de-couple the concurrent operation of the Pd—Ni chemiresistor 102 andthe hydrogen-sensing FET 104 of the H2SCAN sensor. As a result, each IHGsensor 100 may comprise a H2SCAN sensor with one of the twohydrogen-detecting mechanisms being activated, or in the alternative,may comprise a new ASIC having only one of the two hydrogen-detectingmechanisms thereon (i.e., Pd—Ni chemiresistor 102 or thehydrogen-sensing FET 104) along with the temperature-compensationcircuitry 106 and the pressure compensation circuitry 108. An example ofa sensor that comprises only the hydrogen-sensing FET is sensor modelno. AS-FHH-400, or sensor model no. AS-FHH-450, both manufactured byAppliedSensor of Linköping, Sweden.

[0054] The IHG sensor 1000 in the protection sleeve 2020 is the only IHGsensor 100 that detects the hydrogen level in the immediate outsidephysical environment. This sensor is recessed inside the protectivesleeve 2020 to prevent any damage to the sensor during use.

[0055] Each of the IHG sensors 100 is continuously reporting hydrogenconcentration levels to the controller 26. In monitoring the hydrogengas flow, the controller 26 checks the data from each IHG sensor 100 tosee if there is a 10% or greater change in hydrogen concentration levelfrom the last reading, which is indicative of a possible leak.

[0056] The monitoring and control system 22 operates on safety limitswhich are in turn based on the lower explosive limit (LEL) of hydrogenin ambient air. As mentioned earlier, hydrogen is a flammable gas thatcan be ignited in ambient air at minimum concentration of 40,000 ppm or4 volume %, i.e., the LEL of hydrogen in ambient air. The first safetylevel is defined as 10,000 ppm or 25% LEL (also referred to as 1 volume%). A second safety limit is 20,000 ppm or 50% LEL. In view of this, themonitoring and control system 22 takes action via the controller 26activating the alarm 28 and/or controlling the shutoff valves 4A.

[0057] For those IHG sensors 100 monitoring the outside, immediate openair environment, i.e., IHG 1000, this sensor typically operates inatmospheric pressure (e.g., 0.8-1.2 bars) in the temperature range of−40° C. to 85° C. Where the hydrogen concentration level detected bythis sensor 1000 is within the “background hydrogen level-open air(BHL-OA)”, e.g., 50-250 ppm v/v (with an error of approximately +5 ppm),the operating condition is “normal”. On the other hand, a leak can bemanifested in several ways as detected by the IHG sensor 1000:

[0058] (1) if the IHG sensor 1000 detects at least three consecutivehydrogen levels that are increasing (where each newly-detected hydrogenlevel ≧10% than the last detected hydrogen level, i.e., ≧10%/point);

[0059] (2) if the IHG sensor 1000 detects a “major” hydrogen level jump,e.g., 100% hydrogen of BHL-OA (e.g., from 250 ppm to 99.5% hydrogen);

[0060] (3) detecting >10,000 ppm (25% of LEL) in one reading;

[0061] (4) detecting >20,000 ppm (50% of LEL) in one reading; or

[0062] (5) detecting >40,000 ppm (LEL STATE) in one reading.

[0063] In processing this sensor's signals, the processor 26:

[0064] (1) considers hydrogen level readings from IHG sensor 1000 thatare ≦10,000 ppm v/v (25% of LEL) as normal operating conditions;

[0065] (2) activates an alarm and shuts down the particular hydrogentransfer for that nozzle whose IHG sensor 100O hydrogen levels ≧10,000ppm (25% of LEL); however, adjacent nozzle hydrogen transfers continue.

[0066] For those IHG sensors 100 monitoring conditions inside the nozzle20, these sensors (100A-100N and 100P) typically operate in atmosphericpressure (e.g., 0.8-1.2 bars) in the temperature range of −40° C. to 85°C. Where the hydrogen concentration level detected by these sensors100A-100N and 100P is within the “background hydrogen level-insidenozzle (BHL-IN)”, e.g., 50-5000 ppm v/v (with an error of approximately±5 ppm), the operating condition is “normal”. On the other hand, a leakcan be manifested in several ways as detected by these IHG sensors100A-100N and 100P:

[0067] (1) if any of these sensors 100A-100N and 100P detects at leastthree consecutive hydrogen levels that are increasing (≧10%/point) over30 seconds;

[0068] (2) if any of these sensors 100A-100N and 100P detects a “major”hydrogen level jump, e.g., 100% hydrogen of BHL-IN (e.g., from 5000 ppmto 99.5% hydrogen);

[0069] (3) if any of these sensors 100A-100N and 100P detects >10,000ppm (25% of LEL) in one reading;

[0070] (4) if any of these sensors 10A-100N and 100P detects >20,000 ppm(50% of LEL) in one reading; or

[0071] (5) if any of these sensors 100A-100N and 100P detects >40,000ppm (LEL STATE) in one reading.

[0072] In processing these sensors' signals, the processor 26:

[0073] (1) considers hydrogen level readings from all sensors 100A-100Nand 100P that are <10,000 ppm v/v (25% of LEL) as normal operatingconditions;

[0074] (2) activates an alarm and shuts down the particular hydrogentransfer for that nozzle if any IHG sensor 100A-100N and 100P hydrogenlevel ≧10,000 ppm (25% of LEL); however, adjacent nozzle hydrogentransfers continue.

[0075] As mentioned earlier, it is within the broadest scope of thepresent invention to include a nozzle for transferring liquid hydrogenfrom one container to another container which can detect leaks andinform the monitoring and control system 22. By way of example only, anozzle 320 for transferring liquid hydrogen is shown in FIG. 8, which issimilar to the nozzle disclosed in European Patent Application EP 0574811 entitled “Method for Cooling a Storage Container”. In particular, asshown in FIG. 8, a hydrogen source tank 1B is connected to the inputside of the nozzle housing 302 through a pump 401, a cryogenic checkvalve 403 and a vacuum-insulated hose 3B. The distal end 303 of thenozzle housing 302 comprises a cryogenic shut-off member 308. The distalend 303 of the nozzle housing 302 couples to a coupling port 314 whichcomprises a coupling socket 305 whose distal end 307 also comprises acryogenic shut-off member 315. When these two distal ends 303/307 arecoupled together at plane P, they form a pressure-tight housing. Theoutput side of the coupling socket 305 is coupled to an opening in thestorage container 2B via another vacuum-insulated hose 5B. Although notshown in FIG. 8, the controller 26 also controls the operation of thecryogenic valve 403 and pump 401.

[0076] The open end of a line-terminating tube 333 is slidably (thedouble-headed arrow 309 indicates the possible movement of theline-terminating tube 333) and concentrically-positioned within theinput end of the nozzle housing 302 of the nozzle 320; the other end ofthe line-terminating tube 333 is coupled to the vacuum-insulated hose3B. The line-terminating tube 333 comprises an output 306 for deliveringliquid hydrogen and a projection 334, the purpose of which is discussedbelow. A relief line or vent stack 6A and cryogenic check valve 6B arecoupled to the vacuum-insulated hose 3B. Each of the shut-off members308/315 comprises a bore 313 and 317 that permit the line-terminatingtube 333 to pass therethrough. When the line-terminating tube 333 isaxially-positioned through the bores 313/317, a ball 318 is driven offits seat 319 against the bias of a spring 321, thereby allowing liquidhydrogen to pass through the nozzle output 306 and into thevacuum-insulated house 5B. Thus, liquid hydrogen is delivered to thestorage container 2B. An output line 416 of the storage container 2Bincludes a heat exchanger 416 for warming the stored liquid hydrogenbefore use. Furthermore, as liquid hydrogen flows towards the storagecontainer 2B from the nozzle 320 following the NFP, hydrogen gas fromthe storage container 2B exhausts back through the vacuum-insulated hose5B towards the nozzle 320 (hence, the double-headed arrow 9) through thecoupling port 314/nozzle 320 and safely out of the relief line 6A.

[0077] Because the operating conditions of transferring liquid hydrogenis different than transferring hydrogen gas, the methodology indetecting leaks is different. In particular, unlike the transfer ofhydrogen gas, the transfer of liquid hydrogen involves only lowpressures and the temperature during transfer of the liquid hydrogen isextremely low, e.g., approximately −252.8° C. Under normalcircumstances, the nozzle 320 comprises 100% hydrogen. However, whenthere is no transfer of liquid hydrogen occurring, any of the cryogeniccomponents, e.g., the shut-off members 406/408, may begin to leak,thereby allowing allow air to enter, possibly resulting in either oxygenor nitrogen freezing in the storage container 2B. Because it is mucheasier to detect a certain oxygen concentration in the liquid hydrogenflow, than it is detect a slight change in the hydrogen concentration,e.g., a change between 99.9% and 100% H₂, an oxygen sensor 400 ispositioned inside the nozzle 320, preferably in the line-terminatingtube 333, or alternatively, upstream of the liquid hydrogen flow, e.g.,in the vacuum-insulated hose 3B.

[0078] The oxygen sensor 400 (e.g., Microsens' MSGS MGSM3000 O₂monosensor) provides a signal to the controller 26 representative of theoxygen concentration level that it is detecting when the liquid hydrogenis not flowing. Because of the extreme cold temperature of the liquidhydrogen flow, the oxygen sensor 400 does not communicate with thecontroller 26 while liquid hydrogen is flowing; instead, the oxygensensor 400 provides a signal to the controller 26 representative of theoxygen concentration level that it is detecting before the liquidhydrogen begins to flow and then after the flow has stopped. If thesensor 400 detects any oxygen in the nozzle 320 prior to initiating theliquid hydrogen flow, the sensor 400 informs the controller 26 aboutthis detected oxygen level and the controller 26 activates the alarm 28,prevents a transfer system operator (or, if automated, a transfercontroller, not shown) from initiating the liquid hydrogen transfer(e.g., by inhibiting the activation of cryogenic valve 403 and pump 404)and institutes an auto-purge phase to drive out the oxygen. Once theoxygen sensor 400 no longer detects any oxygen in the transfer system,the alarm 28 is de-activated and the transfer system is enabled to beginliquid hydrogen transfer.

[0079] Similarly, once the transfer of liquid hydrogen is completed andthe temperature around the sensor 400 rises to approximately −183° C.,the sensor 400 can begin again detecting for any oxygen that may haveentered the flow path and thereby warn the controller 26 to auto-purgethe flow path (as well as set the alarm 28 and prevent the transfersystem operator, or transfer controller, from initiating another liquidhydrogen transfer) in preparation for the next liquid hydrogen transfer.If there is no oxygen detected, the controller 26 enables the nexttransfer of liquid hydrogen.

[0080] The oxygen sensor 400 (e.g., Microsens' MSGS 3000 monosensor)used therein may comprise a MOS-type construction wherein a metal oxidelayer is doped with metal catalyst and covered with a charcoal/carbonfilter to allow for selectivity of oxygen and to reduce crossinterference. The sensor is deposited on platinum and insulated on aSiO_(x) substrate. This construction can operate in extreme temperatureswhen working under a gas-to-liquid phase of hydrogen. The oxygen sensor400 must be able to recover, after being exposed to −252.8° C. of theNFP of the liquid hydrogen for approximately 2-10 minutes and mustrespond to the gas phase of oxygen. Thus, the oxygen sensor 400 candetect the oxygen concentration at the start of the liquid hydrogentransfer and then again at the end of the transfer, when the gas phasecondition has returned.

[0081] It should be understood that it is within the broadest scope ofthe apparatus and method of the present invention to include thedetermination or derivation of related parameters to detected hydrogenleaks during hydrogen transfer such as leak rate, leak energy, etc.

What is claimed is:
 1. A nozzle for dispensing hydrogen gas from ahydrogen gas source into a container and for detecting hydrogen gasleaks, said nozzle comprising: a housing having a portion that isadapted for coupling to an opening of the container; and at least onesensor that is positioned inside said nozzle, said sensor detecting theconcentration of hydrogen and emitting a signal indicative of theconcentration of hydrogen.
 2. The nozzle of claim 1 wherein said atleast one sensor solely detects hydrogen and operates where no oxygen ispresent.
 3. The nozzle of claim 2 wherein said at least one sensorcomprises a palladium-nickel chemiresistor.
 4. The nozzle of claim 2wherein said at least one sensor comprises a hydrogen-sensing fieldeffect transistor.
 5. The nozzle of claim 2 wherein said at least onesensor comprises a plurality of sensors, each of which solely detectshydrogen and operates where no oxygen is present, each of said sensorsemitting a respective signal indicative of the concentration of hydrogenthat it is detecting, each one of said plurality of sensors beingpositioned at a respective location inside said nozzle.
 6. The nozzle ofclaim 5 wherein each of said plurality of sensors comprises apalladium-nickel chemiresistor.
 7. The nozzle of claim 5 wherein each ofsaid plurality of sensors comprises a palladium-nickel chemiresistor anda hydrogen-sensing field effect transistor, said chemiresistor or saidfield effect transistor being active dependent upon said respectivelocation of said sensor.
 8. The nozzle of claim 5 comprising a shroudsurrounding an output of said nozzle and wherein one of said pluralityof sensors is positioned at said shroud.
 9. The nozzle of claim 5wherein one of said plurality of sensors is positioned inside a wall ofsaid nozzle for detecting hydrogen concentrations in the open airimmediately-adjacent said nozzle.
 10. The nozzle of claim 5 including acoupling position between said nozzle and a transfer line from thehydrogen gas source and wherein one of said plurality of sensors ispositioned inside said nozzle at said coupling position.
 11. The nozzleof claim 10 wherein said one of said plurality of sensors that ispositioned inside said nozzle at said coupling position comprises ahydrogen-sensing field effect transistor.
 12. A method for detectinghydrogen gas leaks during the transfer of hydrogen gas from a hydrogengas source into a container, said method comprising the steps of:providing a nozzle, coupled at one end to a transfer line from thehydrogen gas source, and having an output at its other end; positioningat least one sensor inside said nozzle, said at least one sensoremitting a signal indicative of the concentration of hydrogen it isdetecting while hydrogen is being transferred; coupling said at leastone sensor to a controller, said controller receiving said signalindicative of the concentration of hydrogen; coupling said output end ofsaid nozzle to an opening of the container; initiating transfer ofhydrogen gas from the hydrogen gas source to the container; and alertingan operator or shutting off the transfer of hydrogen gas, by saidcontroller, whenever said controller determines that said receivedsignal has reached or exceeds a predetermined hydrogen concentration.13. The method of claim 12 wherein said step of positioning at least onesensor inside said nozzle comprises positioning at least one sensorinside said nozzle that detects only hydrogen and operates where nooxygen is present.
 14. The method of claim 13 wherein said step ofalerting an operator or shutting off the transfer of hydrogen gascomprises the steps of: coupling said controller to a control valvecoupled between the transfer line and said nozzle; and automaticallyshutting down the transfer of hydrogen gas by said controller activatingsaid control valve when said predetermined hydrogen concentration isreached or exceeded.
 15. The method of claim 11 wherein said step ofpositioning at least one sensor inside said nozzle comprises: locating aplurality of sensors inside said nozzle at respective locations therein;and coupling each of said plurality of sensors to said controller sothat said controller receives a respective signal indicative of thehydrogen concentration that each of said sensors is detecting.
 16. Themethod of claim 15 wherein said step of locating a plurality of sensorsinside said nozzle at respective locations therein comprises positioninga plurality of sensors inside said nozzle and wherein each one of saidplurality of sensors detects only hydrogen and operates where no oxygenis present.
 17. The method of claim 16 wherein said step of locating aplurality of sensors inside said nozzle comprises locating one sensor ata shroud that surrounds an output of said nozzle.
 18. The method ofclaim 16 wherein said step of locating a plurality of sensors insidesaid nozzle comprises locating one sensor inside a wall of said nozzlefor detecting a hydrogen concentration of the open airimmediately-adjacent said nozzle.
 19. The method of claim 16 whereinsaid step of locating a plurality of sensors inside said nozzlecomprises locating one sensor at a coupling location between said nozzleand a transfer line from said hydrogen gas source.
 20. A hydrogen gastransfer monitoring and control system for dispensing hydrogen gas froma hydrogen gas source into a container and for responding to hydrogengas leaks, said monitoring and control system comprising: at least onenozzle that is coupled to a hydrogen gas source via a transfer line andcontrol valve, said nozzle comprising: a housing having a portion thatis adapted for coupling to an opening of the container; and at least onesensor that is positioned inside said nozzle, said sensor detecting theconcentration of hydrogen and emitting a signal indicative of theconcentration of hydrogen; and a controller, electrically-coupled tosaid at least one sensor and coupled to said control valve, saidcontroller alerting personnel and/or controlling said control valvewhenever said controller determines that said signal has reached orexceeds a predetermined hydrogen concentration.
 21. The hydrogen gastransfer monitoring and control system of claim 20 wherein said at leastone sensor solely detects hydrogen and operates where no oxygen ispresent.
 22. The hydrogen gas transfer monitoring and control system ofclaim 21 wherein said at least one sensor comprises a palladium-nickelchemiresistor.
 23. The hydrogen gas transfer monitoring and controlsystem of claim 21 wherein said at least one sensor comprises ahydrogen-sensing field effect transistor.
 24. The hydrogen gas transfermonitoring and control system of claim 21 wherein said at least onesensor comprises a plurality of sensors wherein each of said sensorsemits a respective signal indicative of the concentration of hydrogenthat it is detecting, each one of said plurality of sensors beingpositioned at a respective location inside said at least one nozzle. 25.The hydrogen gas transfer monitoring and control system of claim 24wherein each one of said plurality of sensors solely detects hydrogenand operates where no oxygen is present.
 26. The hydrogen gas transfermonitoring and control system of claim 25 wherein each of said pluralityof sensors comprises a palladium-nickel chemiresistor.
 27. The hydrogengas transfer monitoring and control system of claim 25 wherein each ofsaid plurality of sensors comprises a hydrogen-sensing field effecttransistor.
 28. The hydrogen gas transfer monitoring and control systemof claim 25 wherein each of said plurality of sensors comprises apalladium-nickel chemiresistor and a hydrogen-sensing field effecttransistor, said chemiresistor or said field effect transistor beingactive dependent upon said respective location of said sensor.
 29. Thenozzle of claim 24 comprising a shroud surrounding an output of saidnozzle and wherein one of said plurality of sensors is positioned atsaid shroud.
 30. The nozzle of claim 24 wherein one of said plurality ofsensors is positioned inside a wall of said nozzle for detectinghydrogen concentrations in the open air immediately-adjacent saidnozzle.
 31. The nozzle of claim 24 including a coupling position betweensaid nozzle and a transfer line from the hydrogen gas source and whereinone of said plurality of sensors is positioned inside said nozzle atsaid coupling position.
 32. The nozzle of claim 31 wherein said one ofsaid plurality of sensors that is positioned inside said nozzle at saidcoupling position comprises a hydrogen-sensing field effect transistor.33. A nozzle for use in a transfer system for dispensing liquid hydrogenfrom a liquid hydrogen source into a container and for detecting theundesirable entry of oxygen into the system, said nozzle comprising: ahousing having a portion that is adapted for coupling to an opening ofthe container; and an oxygen sensor, positioned inside said nozzle, fordetecting the concentration of oxygen when the liquid hydrogen is notflowing, said sensor emitting a signal indicative of the concentrationof oxygen.
 34. The nozzle of claim 33 wherein said oxygen sensor ispositioned inside said nozzle such that it is exposed to a normal flowpath of the liquid hydrogen.
 35. A method for detecting the undesirableentry of oxygen into a transfer system that transfers liquid hydrogenfrom a liquid hydrogen source into a container, said method comprisingthe steps of: providing a nozzle, coupled at one end to a transfer linefrom the liquid hydrogen source, and having an output at its other end;positioning an oxygen sensor inside said nozzle and coupling said sensorto a controller; coupling said output end of said nozzle to an openingof the container; emitting a signal, by said oxygen sensor, indicativeof the concentration of oxygen in the transfer system before liquidhydrogen begins transferring, said signal being received by saidcontroller; and preventing the transfer of liquid hydrogen until theoxygen is removed from the transfer system.
 36. The method of claim 35further comprising the step of said controller activating an auto-purgephase to drive out the oxygen from the system.
 37. The method of claim35 further comprising the step of said controller activating an alarm toalert a transfer system operator.
 38. The method of claim 36 furthercomprising step of enabling the transfer of liquid hydrogen once saidoxygen sensor no longer detects any oxygen.
 39. The method of claim 38wherein once the desired amount of liquid hydrogen is transferred andthe liquid hydrogen flow is terminated, said method further comprisesthe steps of: emitting a signal, by said oxygen sensor, indicative ofthe concentration of oxygen in the transfer system, said signal beingreceived by said controller; and preventing the transfer of liquidhydrogen until the oxygen is removed from the transfer system.
 40. Anozzle for use in a transfer system for dispensing liquid hydrogen froma liquid hydrogen source into a container and for detecting theundesirable entry of oxygen into the system, said nozzle comprising: ahousing having a portion that is adapted for coupling to an opening ofthe container and another portion coupled to a transfer line from theliquid hydrogen source, wherein the transfer line comprises an oxygensensor therein, said oxygen sensor detecting the concentration of oxygenwhen the liquid is not flowing and wherein said sensor emits a signalindicative of the concentration of oxygen.